1. Field of the Invention
This invention pertains to treatments of disorders associated, at least in part, with neural activity. These may include, without limitation, gastrointestinal, pancreo-biliary, cardio-respiratory and central nervous system disorders (including neurological and psychiatric, psychological and panic disorders). More particularly, this invention pertains to treatment of such disorders through management of neural impulse stimulation and blocking.
2. Description of the Prior Art
As disclosed in the parent applications and their related international patent application Ser. Nos. PCT/US2004/002847; PCT/US2004/002841 and PCT/US2004/002849 (all incorporated herein by reference), a wide variety of disorders can be treated by blocking neural impulses on the vagus nerves. The blocking can be used as a therapy by itself or used in combination with traditional electrical nerve stimulation. The disorders to be treated include, without limitation, functional gastrointestinal disorders (FGIDs) (such as functional dyspepsia (dysmotility-like) and irritable bowel syndrome (IBS)), gastroparesis, gastroesophageal reflux disease (GERD), inflammation, discomfort and other disorders. Also, the blocking therapy has described application to central nervous system treatments.
Treatments of gastrointestinal diseases through nerve stimulation have been suggested. For example, U.S. Pat. No. 6,238,423 to Bardy dated May 29, 2001 describes a constipation treatment involving electrical stimulation of the muscles or related nerves of the gut. U.S. Pat. No. 6,571,127 to Ben-Haim et al. dated May 27, 2003 describes increasing motility by applying an electrical field to the GI tract. U.S. Pat. No. 5,540,730 to Terry, Jr. et al., dated Jul. 30, 1996 describes a motility treatment involving vagal stimulation to alter GI contractions in response to a sense condition indicative of need for treatment. U.S. Pat. No. 6,610,713 to Tracey dated Aug. 26, 2003 describes inhibiting release of a proinflammatory cytokine by treating a cell with a cholinergic agonist by stimulating efferent vagus nerve activity to inhibit the inflammatory cytokine cascade.
The present invention is an improvement upon a neural blocking therapy as described in the parent applications. Suggestions have been made to block nerves in very specific ways. For example, U.S. Pat. No. 5,188,104 to Wernicke et al. dated Feb. 23, 1993 describes an attempt to inhibit a subset of nerve fibers in the vagus. Specifically, the patent suggests selectively blocking C-fibers of the vagus at a 40 Hz signal. The maximum frequency discussed in this patent is a 150 Hz frequency. To avoid undesired effects of vagal stimulation on organs not targeted by the stimulation, U.S. Pat. No. 6,684,105 to Cohen et al. dated Jan. 27, 2004 describes the use of collision blocks to suppress antidromic effects of stimulation signals. Both of these blocking techniques have significant drawbacks. Subselection of fibers is very difficult in practice. Collision blocking results in a signal being propagated in both afferent and efferent directions. The parent applications teach application of full cross-section neural block to inhibit action potentials across all nerve fibers at a blocked site and thereby blocking both afferent and efferent signals.
The present invention is an improvement upon a neural blocking to avoid antidromic influences during stimulation or to otherwise down-regulate nerve activity. Cryogenic nerve blocking of the vagus is described in Dapoigny et al., “Vagal influence on colonic motor activity in conscious nonhuman primates”, Am. J. Physiol., 262: G231-G236 (1992). Electrically induced nerve blocking is described in Van Den Honert, et al., “Generation of Unidirectionally Propagated Action Potentials in a Peripheral Nerve by Brief Stimuli”, Science, Vol. 206, pp. 1311-1312. An electrical nerve block is described in Solomonow, et al., “Control of Muscle Contractile Force through Indirect High-Frequency Stimulation”, Am. J. of Physical Medicine, Vol. 62, No. 2, pp. 71-82 (1983) and Petrofsky, et al., “Impact of Recruitment Order on Electrode Design for Neural Prosthetics of Skeletal Muscle”, Am. J. of Physical Medicine, Vol. 60, No. 5, pp. 243-253 (1981). A neural prosthesis with an electrical nerve block is also described in U.S. Patent Application Publication No. US 2002/0055779 A1 to Andrews published May 9, 2002. A cryogenic vagal block and resulting effect on gastric emptying are described in Paterson C A, et al., “Determinants of Occurrence and Volume of Transpyloric Flow During Gastric Emptying of Liquids in Dogs: Importance of Vagal Input”, Dig Dis Sci, (2000); 45:1509-1516.
Constant nerve blocking (through constant blocking signal application) can be undesirable. Such a treatment can have high power requirements. Furthermore, a complete down-regulation of a nerve can be undesirable since the nerve's desirable functions are also interrupted. It would be desirable to more fully control the degree of down-regulation of a nerve to achieve a desired therapy while minimizing undesired effects of complete or constant down-regulation.